VADs are commonly used therapeutic devices yet accounted for 18,000 blood stream infections in American ICUs in 2009, according to the CDC, which also reports a mortality rate of 12-25%. MMWR Morb. Mortal Wkly. Rep. 2011; 60:243-248. In the same article, the CDC attributes additional blood stream infections and deaths to VAD use in regular hospital rooms and out-patient care.
If not properly maintained the VADs, which include peripheral catheters and central venous catheters, can become sealed with blood clots or spread infection. To ensure VADs are used properly and do not become sealed or infected, protocols have been developed. These protocols include sterilizing the VAD and the flushing the catheter with a flush solution. VAD protocols usually recommend flush procedures be performed after catheter placement, before fluid infusion, and before and after drug administration, blood sampling, transfusions and parenteral nutrition. The goal of these flush procedures is to confirm catheter patency, avoid drug incompatibilities, ensure the complete drug dose administration, prevent thrombus formation and minimize the risk of blood stream infections. Before each flush procedure is performed, the VAD should be sterilized. A recent study reported that 30% of the time, there is no effort to sterilize the VAD prior to flushing and when an attempt to sterilize the VAD it often did not fully meet aseptic practices.
Catheters are flushed using syringe assemblies filled with various fluids. In some cases, different fluids are injected sequentially in accordance with the protocol. For example, a saline solution followed by an anticoagulant such as heparin. The size of the syringe used to flush LV. lines varies by various factors including the size and length of the catheter. Typically syringes of 1 ml, 3 ml, 5 ml and 10 ml volume are used.
It is important in the flush procedure not to draw blood back into the catheter where it can clot and seal the catheter, commonly referred to as “reflux”. In order to prevent blood reflux into the catheter the user is encouraged to maintain a positive pressure in the line during the flush procedure. This may involve clamping the IV line and Withdrawing the syringe and cannula from the LV. port while still applying pressure to the syringe plunger rod during the flush procedure. When using a syringe with an elastomeric stopper, the stopper is often compressed when it contacts the distal end of the syringe barrel at the completion of the flush procedure. When a user relieves the pressure to the plunger after the flush procedure is completed, the stopper will expand back to its normal size thereby withdrawing liquid from the catheter into the syringe barrel. This is undesirable, since it can cause blood to enter the catheter at the catheter distal end (reflux) where it will remain stationary until the next time the VAD is used.
IV lines are now being flushed by a wide variety of health care workers, not just those who in the past were dedicated to catheter maintenance. In the case of out-patient care, the patients themselves may even flush their own catheters. These less experienced persons might prematurely release the compressive force on the stopper or use excessive force which would deform the stopper, either which may draw blood into the catheter and cause reflux of blood. Consequently, there is a need for flush syringe assemblies which promote sterilizing the VAD and help reduce or eliminate reflux of blood during the flushing procedure even if flush protocols are not precisely followed.